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Abstract

Aquaculture provides the means to meet the growing sea food demand, while enriching the local ecosystems through excess feed and faecal matter outputs. Analyzing the quality and quantity of material exiting the farms and its uptake by surrounding invertebrates highlights the effectiveness of muti-trophic, co-culturing systems where waste from one species is recycled as food for adjacent species. This thesis describes organic throughput of juvenile Atlantic cod (Gadus morhua) land-based tanks and uptake of organic constituents by invertebrates surrounding Atlantic salmon (Salmo salar) farms. -- The land-based tank output showed significant lipid and fatty acid increases in outflow compared to inflow (p<0.020) for the breakdown indicator free fatty acid (FFA), the markers of zooplankton and subsequent indicators of the feed, 20:1ω9 and 22:1ω11, and the essential fatty acid DHA(docosahexaenoic acid, 22:6ω3). Scaling to an 1880 tonne Atlantic cod farm showed 3170±870 kg/day particulate dry weight and 4.7±1.7 kg/day DHA exiting the farms. Based on the amount of DHA required per mussel, the scaled amount of DHA could theoretically support 1400 tonnes of mussels assuming optimal consumption of the available DHA. This relates to mussels' role in multi-tropic co-culturing systems as they could assimilate valuable compounds that would otherwise be lost. -- Regression analysis of particle uptake by invertebrates surrounding multiple aquaculture sites in coastal British Columbia showed a decrease in wet weight for mussels with increasing distance from the farm. There was also an increase in DHA in molluscs combined as well as mussels alone. Principal components analysis showed a similar trend with DHA being higher in molluscs further away from the farm. In addition, bacterial fatty acid markers were higher in molluscs further from the farm except for the individual bacterial fatty acid, 18:1ω7, which remained higher closer to the farm for molluscs combined, mussels and whelks, and mussels alone; however, not for limpets alone. Additionally, a breakpoint was found for DHA in mussels at 339 m with lower DHA proportions closer to the farm. However, of the DHA present, mussels had significantly higher amounts compared to other molluscs again relating to their use in multi-trophic aquaculture.